Download - Module 8 Survey sample builder
Module 8 Survey sample builder (SSB)
TAS
Global Programme to Eliminate Lymphatic Filariasis (GPELF)
Training in monitoring and epidemiological assessment of mass drug administration for eliminating lymphatic filariasis
Module 8 Survey sample builder
Module 8 Survey sample builder (SSB)
Learning objectives
Slide 2
By the end of this module, you should understand:
1. how to use the survey sample builder to: determine the survey design select random clusters and children or households
2. the protocol for TAS
Module 8 Survey sample builder (SSB)
Overview
The survey sample builder Determining the survey design Selecting randomized clusters Selecting randomized children or households Protocol for TAS
Slide 3
Module 8 Survey sample builder (SSB)
Survey sample builderThe survey sample builder is a Microsoft Excel tool that can be used to (i) automate calculations for determining the appropriate survey design and (ii) facilitate random selection of clusters and children or households from a list of randomized numbers.
Slide 4
School
CensusCluster-based Systematic
School
Child Child
Community
CensusCluster-based Systematic
Enumeration area
Household Household
Survey design
Random selection
Sample size and critical cut-off
Evaluation unit
Module 8 Survey sample builder (SSB)
Preparation before sample selectionSchool-based survey
Slide 5
Communicate with the ministry of education to obtain a comprehensive list of all primary schools in the defined EU. Ideally, the list of schools will be ordered according to
geographical proximity rather than alphabetically. This will allow better geographical representation of the selected schools in the EU.
Obtain an average non-response rate for the schools in the EU, if available. The non-response rate gives an estimate of the non-participant
rate and should include school absenteeism, refusals and inability to collect sufficient blood for diagnostic testing.
Module 8 Survey sample builder (SSB)
Preparation before sample selectionCommunity-based household survey
Slide 6
Census enumeration areas are recommended as clusters if cluster sampling is used; enumeration areas are usually the smallest areas for which census data are available.
Obtain a list of all enumeration areas in the EU. Ideally, the enumeration areas will be listed according to
geographical proximity rather than alphabetically.
Obtain enumeration area census maps. These maps can often be obtained from the census department
or bureau of statistics. A fee may be charged to obtain these maps.
Module 8 Survey sample builder (SSB)Slide 7
Available for download at http://www.filariasis.us./resources.html
Determining the survey design
Module 8 Survey sample builder (SSB)Slide 8
Determining the survey design
Module 8 Survey sample builder (SSB)Slide 9
Determining the survey design
Module 8 Survey sample builder (SSB)Slide 10
Survey sampling method determined by data entered into
programme
Determining the survey design
Module 8 Survey sample builder (SSB)
Once the appropriate survey design has been determined, the survey sample builder facilitates selection of clusters and children or households by generating a list of randomized numbers.
Slide 11
School
CensusCluster-based Systematic
School
Child Child
Community
CensusCluster-based Systematic
Enumeration area
Household Household
Survey design
Random selection
Sample size and critical cut-off
Evaluation unit
Selecting randomized clusters and children or households
Module 8 Survey sample builder (SSB)
Selecting randomized clusters
Slide 12
Cluster sampling requires a minimum of 30 schools or enumeration areas in which children are selected.1. Obtain a comprehensive list of all primary sampling units (i.e.
schools, enumeration areas) in the evaluation unit.
2. Number them, preferably in order of geographical proximity as opposed to alphabetical order to achieve better geographical distribution of the evaluation unit.
3. Once all sampling units have been assigned a number, click the “Randomize” button.
4. Once the survey design has been determined, a list of random numbers (e.g. 10, 23, 36, 49 …) is generated. Select the schools or enumeration areas in the list according to the random numbers (i.e. 10th, 23rd, 36th, 49th …).
Module 8 Survey sample builder (SSB)
Selecting randomized clusters
Slide 13
Total number of EAs: 487No. of EAs (clusters) to be sampled: 37
Directions: Obtain a comprehensive list of all the primary sampling units (i.e. Schools or EAs) in the EU and number them, preferably in order of geographic proximity. Once all sampling units have been assigned a number, double check that the values listed below are correct and click the "Randomize" button. When you are finished you can click "Return to Previous Page" to go back.
Randomize
Return to Previous Page
A list of random numbers can be generated to facilitate the selection of clusters to be included.
The following schools or enumeration areas have been selected for your study: 10
233649627689
102….
Module 8 Survey sample builder (SSB)
Selecting randomized clusters
Slide 14
Selection of 5–10 additional clusters is recommended as a contingency plan if the sample size falls considerably short of the target after all the clusters have been surveyed. Additional clusters should be selected from a list of all remaining
clusters, excluding those that have already been chosen. The same random selection process used for the original clusters should be used.
The survey sample builder allows selection of additional clusters.
Module 8 Survey sample builder (SSB)
Selecting randomized children or households
Slide 15
After selection of randomized clusters in cluster sampling or after choosing systematic sampling, children (in school-based surveys) or households (in community-based surveys) are selected randomly.
The survey sample builder calculates the appropriate sampling interval.
The survey sample builder also calculates a random starting number and the sampling interval (inverse of the sampling fraction) to generate two numbered lists (A and B) to guide the actual selection of schoolchildren or households
For school-based surveys, lists A and B are used to select the children to be tested.
For community-based surveys, lists A and B are used to select the houses in the enumeration areas to be sampled.
Module 8 Survey sample builder (SSB)
Selecting randomized children or households
Slide 16
In this example, the team chose list A; therefore, the first, third, fourth, fifth … house on the list or map will be selected.
Every 6- and/or 7-year-old child in the house should be tested. The same list should be used throughout the survey.
Module 8 Survey sample builder (SSB)
Example 1
Slide 17
Net school enrolment ratio: 78%
Primary vector: Culex
Population of students in target grades: 18 945
Total number of primary schools: 386
Estimated non-response rate: 15%
Module 8 Survey sample builder (SSB)
Example 1. Survey design
Slide 18
Country: Example 1Name of EU: Example 1Primary Vector: Anopheles, Culex, or Mansonia
Demographic data on EU (provided by user)
Population of students in target grade(s):18,945
Total number of schools: 386 Avg. number of students in target grade(s) per school: 49*Note, if any of the above information is incorrect, click on the 'Back to "Start Here"' button and then click 'edit EU information'
Cluster Survey of School Entrants Survey Sampling Methodology (calculated by program)
Sample Size for Cluster Design 1,552Number of Clusters1 38
Sampling Fraction (of children within the schools)1Test all children in the target grade(s)
Sampling Interval (of children within the schools)1N/A
Critical Cut-off (maximum # positive ICT/Brugia Rapid results allowable for country to "Pass") 18
1Based on a 15% absentee rate
Module 8 Survey sample builder (SSB)
Example 1. Randomized cluster selection
Slide 19
Directions: Obtain a comprehensive list of all the primary sampling units (i.e. schools or enumeration areas) in the evaluation unit, and number them, preferably in order of geographical proximity. Once all sampling units have been assigned a number, double-check that the values listed below are correct, and click the "Randomize" button. When you have finished, you can click "Return to previous page”.
Total number of schools: 386No. of schools (clusters) to be sampled: 38
The following schools have been selected for your study:8
1829394959697990
100110
…
Module 8 Survey sample builder (SSB)
Example 1. Randomized cluster selection
Slide 20
School name1 Woodridge Elementary2 Lakeside Elementary3 Shadow Rock Elementary4 Austin Elementary5 Idlewood Elementary6 Henderson Mill Elementary7 Stone Mill Elementary8 Rockland Elementary9 Sage Elementary
10 Oak Grove Elementary11 Brockett Elementary12 Princeton Elementary13 Chestnut Elementary14 Rockbridge Elementary15 Dresden Elementary16 Midvale Elementary17 Columbia Elementary18 Pine Ridge Elementary19 Flatrock Elementary20 Snapfinger Elementary…
The following schools have been selected for your study:
81829394959697990
100110
…
Module 8 Survey sample builder (SSB)
Example 2
Slide 21
Net school enrolment ratio: 68%
Primary vector: Anopheles
Population of students in target grades: 23 128
Total number of enumeration areas: 284
Estimated non-response rate: 15%
Module 8 Survey sample builder (SSB)
Example 2. Survey design
Slide 22
Country: Example 2Name of EU: Example 2Primary Vector: Anopheles, Culex or Mansonia
Demographic data on EU (provided by user)
Population of 6-7 yrs:23,128
Total number of EAs: 284 Avg. population 6-7yrs per EA: 81*Note, if any of the above information is incorrect, click on the 'Back to "Start Here"' button and then click 'edit EU information'
Cluster Survey of Households Survey Sampling Methodology (calculated by program)
Sample Size for Cluster Design 1,552Number of Clusters1 30Sampling Fraction (of children within the EAs)1
0.75Sampling Interval (of children within the EAs)1
1.34Critical Cut-off (maximum # positive ICT/Brugia Rapid results allowable for country to "Pass") 18
1Based on a 15% absentee rate
Module 8 Survey sample builder (SSB)
Example 2. Randomized selection of households
Lists corresponding to the houses selected for sampling out of all houses in the selected enumeration area
The random number used to generate these lists is: List A List B
0.775367533 1 13 24 45 57 68 89 9
11 1012 1213 1315 1416 16… …
1 2 3 4 5 6
10 9 8 71112
Module 8 Survey sample builder (SSB)
Example 3
Slide 24
Net school enrolment ratio: 95%
Primary vector: Aedes
Population of students in target grades: 2 814
Total number of primary schools: 24
Estimated non-response rate: 15%
Module 8 Survey sample builder (SSB)
Example 3. Survey design
Slide 25
Country: Example 3Name of EU: Example 3Primary Vector: Aedes
Demographic data on EU (provided by user)
Population of students in target grade(s):2,814
Total number of Schools: 24
Avg. number of students in target grade(s) per school: 117*Note, if any of the above information is incorrect, click on the 'Back to "Start Here"' button and then click 'edit EU information'
Systematic Sample of School Entrants Survey Sampling Methodology (calculated by program)
Sample Size for Systematic Sample 1172
Sampling fraction (children within each school)1
0.49Sampling interval (children within each school)1
2.04Critical Cut-off (maximum # positive ICT/Brugia Rapid results allowable for country to "Pass") 7
1Based on a 15% absentee rate
Will visit every school in the
evaluation unit
Module 8 Survey sample builder (SSB)
Protocol for TAS
Slide 26
Define EU Determine survey site and sampling strategy Calculate sample size Prepare lists
Schools (school-based survey) Enumeration areas (community-based survey)
Test selected children ICT (areas endemic for W. bancrofti) Brugia RapidTM (areas endemic for Brugia spp.)
Interpret results on basis of critical cut-off
Module 8 Survey sample builder (SSB)
Exercise
Slide 27
Using population data from the evaluation unit(s) defined in the ‘Evaluation unit’ module:
Use the survey sample builder to define:
the appropriate survey design
the sample size needed
the number of clusters needed for the survey
the sampling fraction
the sampling interval
Use the survey sample builder to:
select clusters to be included (if necessary)
generate lists A and B (if necessary)